There is growing awareness of the health benefits to people associated with soluble fiber consumption, especially reductions in blood serum cholesterol, i.e., antihypercholesterolemic benefits. Total dietary fiber ("TDF") comprises both soluble dietary fiber ("SDF") and insoluble dietary fiber ("IDF"). In addition to insoluble fiber, certain whole grain cereal flours contain soluble fiber which predominantly comprises beta glucans. Oats and barley are well known as having relatively high levels of soluble fiber. The SDF content of oat flour ranges from about 3% to 7% depending upon such factors as variety, yield/season, source, etc. The SDF in oats is selectively concentrated in the outermost part of the endosperm close to the bran. Because of this, the oat bran fraction is relatively higher in soluble fiber concentration than whole oats and can range from about 5% to 8%. For this reason, oat bran consumption is enjoying immense and growing popularity. Oat bran is commonly added as a minor constituent to a wide variety of foods and as a major or principal component of various cereal products, both hot cereals and ready-to-eat ("R-T-E") cereals. See U.S. Pat. No. 4,497,840 (issued Feb. 5, 1985 to Gould et al.) entitled Cereal Foods Made From Oats and Method of Making. The art also includes methods for diluting the beta glucan content of oat flour (see U.S. Pat. No. 4,620,981 entitled Process for Preparing a Highly Expanded Oat Cereal Product, issued Nov. 4, 1986 to Gordon et al.). Unfortunately, due to the sudden increase in popularity, oat bran availability is tight and prices are high.
In view of the availability and price of oat bran, it would be desirable to have an alternate concentrated source of soluble flour to oat bran. At present, psyllium seed husk flour (about 85% soluble fiber) has been suggested for use as a soluble fiber additive for a large number of food products. While useful, psyllium is also expensive. Moreover, psyllium is an imported foodstuff. It would be desirable to have a source of concentrated soluble fiber from a domestic or common dried grain, such as barley.
The soluble fiber content of barley is roughly comparable to that of oats and ranges from about 3% to 7%, again depending upon such factors as variety, etc. However, in contrast to oats wherein the oat bran fraction is distinctly higher in soluble fiber, barley bran is not. The soluble fiber distribution in barley is more complex. Barley soluble fiber is concentrated in the cell walls of the endosperm, however, the soluble fiber distribution is more uniform throughout the barley endosperm or grain relative to the soluble fiber distribution in oats. Thus, unlike oat bran, barley bran is not usefully higher in soluble fiber content. Unfortunately then, due to these and other differences between grains, the art's teaching regarding milling and especially oat milling generally fails to provide methods for preparing barley fractions relatively richer (i.e., greater than about 7%) in soluble fiber content. Methods and techniques useful in processing other cereal grains provide little actual useful guidance in this respect due to the distinctive nature of barley.
The prior art, however, does include teachings on one known barley processing method to provide a purified beta glucan content barley fraction. This known processing method involves a wet processing method and is described in U.S. Pat. No. 4,804,545 entitled Production of Beta Glucan Bran, Protein, Oil and Maltose Syrup from Waxy Barley (issued Feb. 14, 1989 to Goering et al.). The wet processing techniques therein described involve improvements in wet barley processing methods described in U.S. Pat. Nos. 4,311,714 and 4,428,967. The improvements reside in a water extraction of the beta glucan from barley flour and involves a sequence of centrifugation steps and further dehydration steps. An advantage of this wet system is that a fraction can be obtained which is very high in its beta glucan content, i.e., is purified as compared to merely concentrating as in the present invention. Unfortunately, the wet milling process has multiple disadvantages. First, the process is complex, and thus both expensive and capital intensive. Due to its highly viscous nature, dehydration steps are especially difficult and energy intensive. Also, no commercial facility now exists which can practice the process on a commercial scale; that is, the method cannot be used with existing milling equipment. Finally, yields are low.
Surprisingly, the present invention overcomes the above disadvantages and provides methods for preparing a concentrated source of barley beta glucan. The present methods comprise dry milling techniques which thus can be practiced at many commercial barley milling facilities. Thus, the present methods provide the surprising benefits of being simple, inexpensive, low energy intensive and do not require construction of new, special purpose commercial facilities. Still another advantage of the present methods is that they can be quickly implemented at existing facilities and so can be used to reduce the present oat bran supply shortage.
The present invention resides in part in the realization that the beta glucan constituent can be separated from barley flour if the barley flour has been sufficiently, but not excessively, size reduced without high shear (e.g., pinmilling) followed by selectively air classifying or sieve screening of the pinmilled barley flour.
It is an advantage of the present invention that all barley varieties can be used, including those more widely available, such as malting barley varieties even though such varieties are low in native SDF.